Currently, an application, such as a browser application (or web browser), can execute external code that is not a part of the application. By way of example, a browser application might execute a web document, or component thereof, which is external to the browser application. A browser application executes a document, e.g., a web document, to generate a user interface display in the browser's user interface. In some cases, the web document can include a reference to a second, separate document provided by an entity other than the entity providing the first document. While it is being executed by a computing device, each document executed by the browser application (and the browser application itself) consumes resources, such as central processing unit (CPU) and memory resources, of the computing device.